Uhf tuner arrangement

ABSTRACT

A continuously variable UHF tuner arrangement is provided wherein a single channel selector shaft is provided with a detent position for each of the 70 UHF television stations and a highly accurate detent mechanism is employed to return the channel selector shaft to any one of the detent positions with extreme accuracy. As a result, the tuning elements of the tuner may be accurately aligned to different UHF stations corresponding to said detent positions and a nonambiguous digital dial arrangement may be employed to indicate to the operator exactly which UHF station is being received. Electronic fine tuning is provided to permit the UHF tuner to be fine tuned independently of the position of the selector shaft.

The present application is a continuation application of patentapplication Ser. No. 600,288, filed on July 31, 1975, and now abandoned,said application Ser. No. 600,288 being a division of my copendingapplication Ser. No. 515,220 filed Oct. 16, 1974 which copendingapplication is a division of application Ser. No. 350,742 filed Apr. 13,1973, said application Ser. No. 350,742 being itself a continuation ofparent application Ser. No. 174,722 filed Aug. 25, 1971, now abandoned.The continuation application Ser. No. 350,742 matured into U.S. Pat. No.3,842,683 on Oct. 22, 1974. Divisional application Ser. No. 515,220matured into U.S. Pat. No. 3,972,241 on Aug. 3, 1976.

The present invention relates to UHF tuner mechanisms, more particularlyto UHF tuning arrangements employing continuously variable UHF tuningelements which are rotatable by means of a common main tuning shaft, andthe invention has for a primary object the provision of a UHF tuningarrangement of this type which is comparable in many respects to thetuning arrangements conventionally used for VHF tuners.

For many years various arrangements have been employed as continuousdrive mechanisms for UHF tuners of the type having a continuouslyrotatable main tuning shaft. Certain arrangements have employed a tuningknob which is connected by means of gears, pinch wheels, cams and camfollowers, ball-planetary mechanisms, or a string drive to the maintuning shaft, with driving ratios which are variable all the way from70:1 to 14:1. Some of these drive arrangements have employed two-speedmechanisms whereby the UHF band may be rapidly covered by motion in onedirection and then a fine tuning operation is performed by rotating thetuning knob in the other direction to tune in the desired UHF station.Two separate knobs have also been employed for such two speed UHF tuningsystems.

The dial arrangements for such continuous drive UHF tuners, whereby thechannel number of the selected UHF station as indicated, have been onlyapproximate and can be called analog-type indicator arrangements sincethe dial moves continuously with the tuning knob. In many instances,these indicators have only certain channel numbers indicated on the dialwith dots in between to show the approximate position of other channels.Calibration accuracy of such dial arrangements is only approximate andthe UHF station to which the UHF tuner is actually tuned varies as muchas plus or minus three UHF channels from the channel numbers indicatedon the dial. Also, in these continuous drive UHF tuner arrangements, thedial moves during the fine tuning operation. The dial indicationachieved with such tuners is very ambiguous and the operator reliesprimarily on his knowledge of which UHF stations are broadcasting in hisarea when he tunes in a given station. Examples of such continuous drivefine tuning arrangements are shown, for example, in Valdettaro U.S. Pat.No. 3,518,888, Badger U.S. Pat. No. 3,446,083, Meadows, et al. U.S. Pat.No. 2,909,934, Krepps U.S. Pat No. 2,665,377 and Sperber U.S. Pat No.2,756,599.

Some attempts were also made at a relatively early date to provide adecade type of dial indication for UHF in conjunction with doublesuperheterodyne type circuits, usually tuned by separate tuning knobs.The double superheterodyne type of UHF tuner was not satisfactorybecause of the use of two local oscillators with its attendantcomplexity and the spurious responses which were encountered in thefield. Examples of such double superheterodyne UHF systems are shown inMachlin U.S. Pat. No. 2,851,593 and Scandurra U.S. Pat. No. 2,785,297.

Other attempts have also been made to provide individual tuning todifferent UHF stations wherein separate groups of tuning elements wereprovided corresponding to a predetermined group of UHF channels. Decadedial arrangements were proposed for certain of these arrangements whichemployed multiple sets of UHF tuning elements. However, with suchmultiple sets of UHF tuning elements it was found to be impossible tocommutate or switch the UHF tuned circuits and reset the tuner back tothe same channel with any degree of accuracy, so that the proposeddecade dial arrangements were unsatisfactory because they would indicatethe wrong channel number. Another problem encountered in such proposeddecade dial arrangements was the inability to manufacture the multiplesets of tuning elements with the precision necessary to substitute oneset for another and have the resultant tuning frequency precise enoughto utilize a fixed number type of dial indicator. Furthermore, UHFtuners employing multiple sets of UHF tuning elements were extremelycomplex and expensive and were completely unsatisfactory from aneconomic standpoint. Examples of such multiple tuning set arrangementsare shown, for example, in Koch U.S. Pat. No. 2,821,624, Rieth U.S. Pat.No. 3,327,221 and Kostecki U.S. Pat. No. 2,886,700.

In February of 1970 the Federal Communications Commission issued aruling requiring that similar types of tuners be used to receive bothUHF and VHF signals in a given television set, insofar as the customeroperation of such tuners is concerned. Furthermore, compliance with thisruling was requested on an increasing percentage of models per year, 10%of the models being required to comply with this ruling in 1971, 40% in1972, 70% in 1973 and 100% in 1974. Since most, if not all VHF tunerspresently employ a fixed stop or detent position for each VHF channeland at least half of these VHF tuners employ so-called memory or presetfine tuning whereby the fine tuning knob is adjusted once for eachchannel and its position thereafter memorized or preset for subsequentselections of that channel, the FCC ruling actually required that UHFtuners be provided with detent positions for UHF stations and, when usedwith preset VHF tuners, that they also embody memory or preset UHF finetuning.

At the time of this ruling by the FCC, various types of detented, presetUHF tuners had been developed and were available in the marketplace. Ingeneral, these detented, preset UHF tuner arrangements provided arelatively small number of detent or stop positions, and in eachposition the tuner was adjustable by an independent, noninteracting finetuning adjustment so that a particular one of the seventy UHF channelscould be selected and assigned to that detent position of the UHF tuner.Individual UHF stations could thus be preset at each detent stop forrepeated access without requiring further fine tuning on the part of theoperator. However, the number of such UHF stations which could beselected was limited to the total number of detent positions available,which was always substantially less than the total number of UHFchannels in the UHF band. UHF tuners of this detented, preset type areshown, for example, in copending Badger application Ser. No. 856,277filed Sept. 9, 1969 and assigned to the same assignee as the presentinvention, which Badger application was abandoned in favor of acontinuation application that matured into U.S. Pat. No. 3,689,853,Schwartz U.S. Pat. No. 3,513,418, Smith U.S. Pat. No. 3,205,720, HartenU.S. Pat. No. 3,474,362, Sperber U.S. Pat. No. 3,459,055, Berenbaum, etal. U.S. Pat. No. 3,447,386 and Kennedy U.S. Pat. No. 3,152,487.

The dial indicator arrangements initially employed with most of thesedetented, preset UHF tuner arrangements were only approximate analogarrangements employing a drum, disc or strip type indicator in whichevery third UHF channel number, or the like, was displayed. Some ofthese detented preset UHF tuner arrangements employed a dial indicatorsystem whereby the exact channel number could be added by the customerat each detent position by means of slip-on or stick-on tags of somespecial design. The total number of exact channel numbers which could beindicated was never equal to the total number of UHF channels in the UHFband, and, in most instances, permitted exact indication of only six UHFchannels. Furthermore, while the stick-on tag, once added by thecustomer, gave a nonambiguous dial indication of a specific UHF channel,any further movement or adjustment of the separate fine tuning knob ofsuch tuners could render such dial indication totally meaningless. Thisis because the fine tuning knob of such tuners covers the entire UHFband and a station different from the one indicated on the dial can betuned in by only a slight readjustment of the memory fine tuning knob.In effect, therefore, such preset dial arrangements were ambiguous inthat the operator was not prevented from tuning in a UHF stationdifferent from the one indicated on the dial. In contradistinction,conventional VHF tuners limit the range of fine tuning so that undernormal receiving conditions the operator is prevented from tuning in achannel different from the one indicated on the VHF dial.

In June of 1970 the Federal Communications Commission clarified itsearlier ruling of February 1970 and at that time stated that the channelindication for UHF tuners should be identical to that employed for VHFtuners. Since all VHF tuners, whether preset or not, indicate the exactchannel being received, UHF tuners were thereby required to have suchexact channel indication, in accordance with the above-describedcompliance time schedule. The detented, preset UHF tuners then availablewere accordingly arranged so that the customer could add on a channeltag at each detented position after the channel had been selected by thecustomer for reception in his area. Furthermore, such add-on tags had tobe inserted by the customer without the use of tools, according to FCCrequirements. This involved customer accessibility to the indicatingelements which carried these tags and required removable knobs, panels,and the like. While such arrangements were tolerable, although obviouslynot satisfactory, in 1971 when a relatively small percentage of thetotal UHF tuner production was required to be comparable with VHFtuners, it was recognized that the means for setting the exact channelindication by the customer provided in these detented, present UHFtuners was not a practical solution, particularly when considered inconnection with the total compliance required in 1974. This isparticularly true because the detented, preset UHF tuners areconsiderably larger and more expensive than a manual VHF tuner and wouldbe economically unsuitable for incorporation in the large volume,low-cost portion of the total line of television receivers of eachmanufacturer. Nevertheless, all detented preset UHF tuners have now beenor are being modified to accept channel tags added by the customer inthe field without the use of tools, which further increases the cost ofthese UHF preset tuning systems and makes this type of tuner veryunattractive for medium and lower-priced television receivers.

Several other UHF tuner arrangements have been heretofore proposed whichprovided a separate detent position for each of the seventy UHF channelsand, in some instances, attempted to provide exact channel indicationfor each UHF station. Examples of such designs are shown, for example,in Dickinson, et al. U.S. Pat. No. 3,492,608, Naber, et al. U.S. Pat.No. 3,307,414, Smith U.S. Pat. No. 3,365,962 and in Zenith tuner manualTm-11, Part No. 923-461. However, due to the poor resettabilitycharacteristics of these designs the dial indication was not comparableto VHF tuners. In conventional manually operated VHF tuners the dialindication is nonambiguous because the resettability and channelalignment specifications for VHF tuners are sufficiently precise thatthe operator is assured that the VHF station which is indicated on thedial is, in fact, the one being received. The 70 detent UHF tuningarrangements heretofore employed, and as exemplified in the above-listedpatents and designs, had such inaccurate detent mechanisms, poorresettability characteristics and nonlinear alignment characteristicsthat exact dial indication was not feasible and in fact would misleadthe operator since he could never be sure that the UHF station indicatedon the dial was the one actually being received. Furthermore, the touchand feel of the detent mechanisms of many of these seventy stop UHFtuners was indistinct to the operator as he grasped the tuning knob andthe torque necessary to turn the tuning knob and angular spacing betweendetent positions were not the same as VHF tuners. Accordingly, there wasa great need at the time of the present invention for a UHF tuningarrangement which would be comparable, insofar as customer operation isconcerned, with VHF tuners, and which could be used to comply with theincreasingly broad requirements of the FCC ruling in 1972 and subsequentyears.

It is, therefore, a further object of the present invention to provide anew and improved UHF tuner arrangement which avoids one or more of theabove-discussed disadvantages of the prior art arrangements.

It is another object of the present invention to provide a new andimproved UHF tuning mechanism for a UHF tuner employing a continuouslyvariable main tuning shaft, wherein the single station selector knob ofthe tuner is provided with a detent arrangement having a detent intervaland touch to the operator which is comparable to conventional VHF tuningmechanisms.

It is a further object of the present invention to provide a new andimproved UHF tuning mechanism for a continuously variable UHF tuningshaft wherein a separate detent position is provided for each of theseventy UHF television stations while at the same time providingsubstantially increased accuracy of resettability of the UHF tuner to aparticular UHF station within the UHF band.

It is yet another object of the present invention to provide a highlyaccurate UHF tuning system utilizing electronic fine tuning.

It is a still further object of the present invention to provide a newand improved UHF tuning mechanism for continuously variable UHF tunerswherein the input shaft which is manipulated by the operator is providedwith 10 equally spaced detent positions and is rotated seven revolutionsto cover the entire UHF band, thereby facilitating direct digitalindication of the channel numbers of all UHF stations in an economicalmanner.

It is another object of the present invention to provide a new andimproved UHF tuning mechanism for a continuously variable UHF tunerwherein a single station selector knob controls selection of individualtelevision stations within the UHF band which are indicated by means oftens and units discs which are mounted concentrically with said knob,thereby to provide an arrangement which is comparable to the digitalindication provided by conventional VHF tuning mechanisms.

It is a further object of the present invention to provide a new andimproved UHF tuning arrangement for continuously variable UHF tunerswherein the channel numbers of individual television stations within theUHF band are indicated by means of a digital indicator of the decadetype and a stop mechanism is provided which positively prevents displayof channel numbers outside the UHF band.

It is another object of the present invention to provide a new andimproved UHF tuning arrangement for continuously variable UHF tunerswherein a simplified decade indicator arrangement is provided forindicating the exact channel number of each television station in theUHF band, said indicator arrangement being positioned outside the frontpanel of the cabinet in which the UHF tuner is positioned in a mannersimilar to many conventional VHF indicator knob arrangements.

It is still another object of the present invention to provide a new andimproved UHF tuning arrangement for continuously variable UHF tunerswherein the channel selector shaft is provided with a separate detentposition for each of the 70 UHF television stations and a fine tuningshaft concentric with said selector shaft is provided for precise tuningto a selected UHF station, said selector shaft and said fine tuningshaft being arranged to receive concentric tuning knobs comprising anouter fine tuning knob connected to said fine tuning shaft and an innerchannel selector knob connected to said channel selector shaft.

It is a further object of the present invention to provide a new andimproved UHF tuning arrangement for continuously variable UHF tunerswherein a channel selector shaft is provided having a separate detentposition for each of the 70 UHF television stations and wherein asimplified and economical indicator dial structure is provided forindicating the detent positions of said channel selector shaft.

It is another object of the present invention to provide a new andimproved UHF tuning arrangement for continuously variable UHF tunerswherein a separate detent position is provided for each of the 70 UHFstations and the frontal area and panel space required thereby isminimized.

It is still another object of the present invention to provide a new andimproved UHF tuning arrangement for continuously variable UHF tunerswherein a separate detent position of the main tuning shaft of the UHFtuner is provided for each of the 70 UHF television stations by means ofa highly accurate detent mechanism which is effective to return the maintuning shaft to a given UHF detent position with extremely goodresettability characteristics.

It is a further object of the present invention to provide a new andimproved UHF tuning arrangement of the continuously variable main tuningshaft type, wherein a linear drive mechanism is employed to rotate themain tuning shaft, the tuning elements carried by said main tuning shaftare accurately aligned to receive a particular UHF channel at each of 70stop positions of said main tuning shaft, and a detent mechanism isprovided which is effective repeatedly to return said main tuning shaftto any one of said aligned UHF stop positions with a high degree ofaccuracy.

It is another object of the present invention to provide a new andimproved UHF tuning arrangement for continuously variable UHF tunerswherein a single channel selector shaft is provided with a detentposition for each of the 70 UHF television stations and facilities areprovided for disabling the AFC control circuit associated with the tunerduring periods when said selector shaft is moved between said detentpositions.

It is still another object of the present invention to provide a new andimproved UHF tuning arrangement for continuously variable UHF tuners,wherein a single channel selector shaft is provided with a detentposition for each of the 70 UHF television stations, fine tuning meansare provided for adjusting the tuning of the continuously variable UHFtuner in each of said detent positions, and facilities are provided fordisabling an AFC control circuit associated with the tuner duringperiods when a fine tuning adjustment is being made.

It is another object of the present invention to provide a new andimproved UHF tuning arrangement for continuously variable UHF tunerswhich provides individual detent positions for each UHF station;nonambiguous direct digital indication for each UHF station is of smallsize and greatly improved reliability, and can be manufactured on a massproduction basis at low cost.

Briefly, in accordance with the present invention, the single channelselector shaft of the UHF tuning mechanism is provided with 10 equallyspaced detent positions so that one revolution of this shaft will cover10 of the 70 UHF stations. A units dial is directly connected to saidselector shaft to provide units digit information concentric with theselector shaft. This units dial drives a decade or tens disc, alsoconcentric with the selector shaft, which carries tens digit informationso that an extremely simple and economical, direct digital indication ofeach UHF channel number is provided. The detented input shaft, which isrotated seven revolutions to cover the entire UHF band, is connected tothe continuously variable main tuning shaft of the UHF tuner through astep-down gearing arrangement comprising a series of loosely meshedspring loaded gears which have a ratio of approximately 14:1 so that theaccuracy with which the selector shaft is detented is magnified ormultiplied by a factor of 14 and the UHF main tuning shaft can be resetto a given UHF stop position with extremely high accuracy. Furthermore,the extremely accurate detent mechanism is employed to achieve thealignment of the tuning elements carried by the main tuning shaft of theUHF very accurately to each of the 70 UHF stations at fixed incrementsof approximately 2.57 degrees of rotation of the main tuning shaftcorresponding to the 70 detent positions of the selector shaft.Preferably, the alignment of the UHF tuning elements is sufficientlyprecise that the tuning never deviates more than plus or minus 3megacycles (i.e., one-half the width of one channel) from the exactfrequency of the station indicated by the digital dial so that anonambiguous dial indication is provided and the tuning operation of theUHF tuner of the present invention, insofar as the customer isconcerned, is quite comparable to the operation of VHF tuners.

The invention, both as to its organization and method of operation,together with further objects and advantages thereof, will best beunderstood by reference to the following specification taken inconnection with the accompanying drawings, in which:

FIG. 1 is a front view of the knob and dial indicator arrangement of theUHF tuner of the present invention;

FIG. 2 is a top plan view of the tuner arrangement of FIG. 1;

FIG. 2A is a fragmentary sectional view taken along the line 2A--2A ofFIG. 2;

FIG. 3 is a bottom view of the tuner arrangement of FIG. 2 with thecover of the UHF tuner partially broken away;

FIG. 4 is a sectional view taken along the line 4--4 of FIG. 2;

FIG. 5 is a fragmentary sectional view taken along the line 5--5 of FIG.2;

FIG. 6 is an exploded view of the elements of the decade dial indicatorarrangement of the present invention and employed in the tunerarrangement of FIG. 2;

FIGS. 7, 8 and 9 are fragmentary plan views of the tuner of FIG. 2showing the UHF stop mechanism in various positions;

FIG. 10 is a fragmentary sectional view taken along line 10--10 of FIG.2;

FIG. 11 is a sectional view taken along line 11--11 of FIG. 4;

FIG. 12 is a sectional view taken along the line 12--12 of FIG. 4;

FIG. 13 is a sectional view taken along the line 13--13 of FIG. 4;

FIG. 13A is a fragmentary sectional view taken along the line 13A--13Aof FIG. 13;

FIG. 14 is a sectional view taken along the line 14--14 of FIG. 4;

FIG. 15 is a fragmentary sectional view, similar to FIG. 4, of analternative tuner arrangement wherein the fine tuning knob is positionedoutside the UHF channel selector knob;

FIG. 16 is an exploded view of the shaft reversal arrangement of FIG.15;

FIG. 17 is a fragmentary sectional view, similar to FIG. 4, of a furtheralternative embodiment of the present invention wherein the fine tuningknob is positioned outside the channel selector knob;

FIG. 18 is a perspective view of the knob arrangement of FIG. 17;

FIG. 19 is a fragmentary perspective view of an alternative embodimentof the invention wherein the AFC circuit of the associated televisionreceiver may be defeated during both UHF fine tuning and UHF channelselecting operations;

FIG. 20 is a longitudinal sectional view taken along the line 20--20 ofFIG. 19;

FIG. 21 is a sectional view taken along line 21--21 of FIG. 20;

FIG. 22 is a fragmentary sectional view similar to FIG. 20 but showingthe UHF fine tuning shaft in tuning position;

FIG. 23 is a perspective view of an alternative embodiment of theinvention wherein there is incorporated a different AFC defeatarrangement for UHF fine tuning and UHF channel selecting operations;

FIG. 24 is a sectional view taken along the line 24--24 of FIG. 23;

FIG. 25 is a schematic diagram of an alternative embodiment of theinvention wherein electronic fine tuning is incorporated;

FIG. 26 is a fragmentary side view similar to FIG. 4, of the electronictuning embodiment of FIG. 25;

FIG. 27 is a fragmentary bottom view, similar to FIG. 3 but on a largerscale, and showing an alternative arrangement for spring loading thetuner main tuning shaft;

FIG. 28 is a perspective view of the loading arrangement of FIG. 27;

FIG. 29 is a top plan view of a further alternative embodiment of theinvention wherein frontal space required by the tuner mechanism isminimized; and

FIG. 30 is a sectional view taken along the line 30--30 of FIG. 29.

Referring now to the drawings, and more particularly to FIGS. 1 to 14,inclusive, thereof the present invention is therein illustrated ascomprising a UHF tuner assembly indicated generally at 30, said assemblycomprising a main base member or chassis 32 having a downturned frontflange portion 34 which is adapted to be secured to the front panel 36of the television receiver cabinet by any suitable means such as thebolts 38. The base member 32 is also provided with a rear downturnedflange 40 which cooperates with the front flange 34 to define a recesswithin which the UHF tuner, indicated generally at 42, is positionedwith the upper wall of this tuner being secured to the base plate 32 bymeans of the screws 44. The base plate 32 is provided with an upstandingrear wall 46, which is conveniently formed from the base plate 32,leaving the opening 48 therein, and the base member 32 is provided witha forward upstanding wall 50 which is also formed from the base member32, leaving the opening 52 therein. The wall portions 46 and 50 areemployed rotatably to mount an inner fine tuning shaft 54 and an outerUHF channel selector shaft 56, these shafts extending parallel to butspaced from the main tuning shaft, or rotor shaft 58 to the UHF tuner42, the rotor shaft 58 extending through suitable clearance openings 58aand 58b in the rear wall of the tuner 42 and the chassis wall 40,respectively. The outer channel selector shaft 56 extends throughsuitable bearing openings in the wall portions 46 and 50, these openingspreferably having sloping edges defining a pair of V-shaped bearingsurfaces for the shaft 56. A U-shaped torsion spring element, indicatedgenerally at 60, is provided with a bight portion 62 which extendsthrough an opening in the rear wall 46 and is positioned in a notch 64in the front wall 50 and extends parallel to the channel selector shaft56. The right-angle front end portion 66 of the torsion spring 60 isbiased into engagement with the selector shaft 56 at a point justforward of the wall 50 and the right-angle rear end portion 68 of thetorsion spring 60 has a V-shaped end portion 70 formed therein (FIG. 5)which is biased into engagement with the adjacent lobe shoulders of aten-position detent wheel 72 which is formed integrally with the rearend portion of the channel selector shaft 56. The right-angle endportions 66 and 68 of the torsion spring 60 thus act also to bias theadjacent portions of the channel selector shaft 66 into engagement withthe V-shaped bearing surfaces provided in the end walls 46 and 50 of thebase plate 32 so that the channel selector shaft 56 is very accuratelypositioned to any one of the 10 detent positions established byengagement of the V-shaped portion 70 of the spring 60 with the detentwheel 72.

The channel selector shaft 56 is thus accurately positioned to 10different detent positions, each representing a UHF station, during onerevolution of the shaft 56 and this shaft is rotated seven revolutionsto cover the entire UHF band of 70 channels. In accordance with animportant aspect of the present invention, a simple concentric dialindicator arrangement is provided, which may be mounted either inside ofor outside of the front panel 36 and is directly supported by and drivenfrom the channel selector shaft 56. In the embodiment of FIGS. 1 to 14,inclusive, this dial indicator arrangement is positioned outside of thefront panel 36. More particularly, a combined channel selector knob andunits indicator disc member, indicated generally at 76 (FIG. 6) ismounted on the forward end portion of the channel selector shaft 56,outside of the front panel 36, by means of a D-shaped opening 78provided in a hub portion 80 of the member 76, the opening 78 conformingto the flat 82 provided on the end portion of the channel selector shaft56 so that the channel selector knob 84 of the member 76 may be graspedby the operator and rotated to turn the channel selector shaft 56 to anydesired UHF position. The member 76 is also provided with a transverselyextending units disc portion 86 which is preferably transparent and hasprinted thereon black numerals 88 corresponding to the ten units digitsof the UHF channel numbers at ten equally spaced positions along theperiphery of the disc portion 86.

A masking member 90, which also acts as a support for the tens disc 92of the dial indicator arrangement, is mounted on the channel selectorshaft 56 ahead of the panel 36 by means of a hub portion 94 which ispositioned on the selector shaft 56, the member 90 being restrained fromrotation about the shaft 56 by means of a rearwardly extending pin 96which is secured thereto and extends through an opening 98 in the frontpanel 36 and into an opening 100 (FIG. 4) in the chassis wall 34. Themasking member 90 is provided with an annular forwardly extending rimportion 102 which acts as a guide or centering arrangement for the tensdisc 92 so as to position this disc concentrically with the axis of theselector shaft 56. A forwardly extending pin 104 is also secured to themasking member 90 and acts as a bearing post for a trip pinion indicatedgenerally at 106 which is rotatably positioned on the post 104. The trippinion 106 is provided with three equally spaced full length teeth 108and three equally spaced teeth of shorter length 110 which arepositioned equidistantly between the teeth 108. The tens disc 92 isprovided with internal gear teeth 112 which are arranged to be in meshwith the teeth 108 and 110 of the trip pinion 106 when the disc 92 ispositioned on the annular rim 102 of the masking member 90. The tensdisc 92 is also preferably transparent and has imprinted thereon aseries of numerals 114 corresponding to the tens digit of the channelnumbers 14 to 83 which are assigned to the UHF band. The tens disc 92 isrotated one tens digit increment for each revolution of the units disc86 by means of a pair of tripper teeth 116 (FIG. 13) which are formed inthe rear side of the units disc 86. More particularly, the disc 86 isprovided with a relatively shallow outer annular recess 118 and a deepercentral recess 120. The tripper teeth 116 are formed at the level of therecess 118 and are positioned so as to contact one of the short teeth110 on the tripper pinion 106 which is positioned between a pair oflonger teeth 108. The longer teeth 108 normally ride on the wall 122 ofthe deeper recess 120 so that the tripper pinion is normally heldagainst rotation during rotation of the units disc 86. As a result,since the tripper pinion 106 is also in mesh with the gear teeth 112 ofthe tens dial 92, the tens dial 92 is prevented from moving as thelonger teeth 108 ride along the shoulder 122.

More particularly, referring to FIG. 12, wherein the surface 122 isshown in dotted lines, it will be seen that one of the short teeth 110extends outwardly beyond the contour of the surface 122 at the level ofthe recess 118 and hence can be engaged by one of the tripper teeth 116.However, the space 124 between the tripper teeth 116 is cut away to thefull depth of the recess 120. Accordingly, when one of the tripper teeth116 engages one of the short gear teeth 110 on the tripper pinion 106,this pinion is rotated while the adjacent long gear tooth 108 rides inthe vertical recess 124. As the units disc 86 is rotated at the tenth ordecade position at which a shift of the tens disc 92 is required, thetrip pinion 106 is rotated by an amount sufficient to bring the next oneof the numerals 114 into the tens digit position. In this position, thenext pair of long gear teeth 108 are positioned properly to ride alongthe surface 122 as the units disc is rotated for the next revolution.

In order that the channel numbers on the tens and units discs 92 and 86may be clearly perceived by the operator when the dial indicator ispositioned outside the front panel 36, the entire front surface of themasking member 90, including the surfaces of the annular rim 102, arepreferably coated with a black, light-absorbing material except in thearea 126 immediately behind the tens and units numerals constituting thechannel number to which the selector knob 56 has been adjusted. The area126 is either uncoated, if the disc 90 is of white translucent material,or, in the alternative, the area 126 may be coated with a brightfluorescent or daylight fluorescent paint of a color having the maximumcontrast with the color of the numerals 88 and 114 on the discs 86 and92, respectively. With such an arrangement, the tens and units numeralsfalling within the area 126 are given maximum contrast for incidentlight from the room while at the same time all of the other numerals onthe discs 86 and 92 are essentially masked from view since they are infront of the darkened or contrasting area of the masking member 90.

While the dial indicator arrangement of the present invention is shownin FIGS. 1 to 14, inclusive, as positioned in front of the front panel36 of the television cabinet, it will be understood that this same dialindicator arrangement may be employed in situations where the dialindicator is to be positioned behind the front panel. Thus, if a frontpanel 36a is positioned in front of the tens and units discs 92 and 86,as indicated in dotted lines in FIG. 4, a viewing window 128 is providedin the panel 36a which matches the viewing area 126 of the disc 90. Withsuch an arrangement all of the other numerals 88 and 114 are blockedfrom view by the front panel 36a. If desired, a dial indicator light maybe positioned behind the disc 92 so as to provide back illumination forthe channel numbers through the window 128. Also, this dial indicatorlight may be energized only when the associated VHF tuner is in the UHFreceiving position so that the UHF channel numbers will become visibleonly during periods of UHF reception, as it will be readily understoodby those skilled in the art. Since the knob structure 76 has toaccommodate the opening 130 in the front panel 36a, the forward knobportion 84 of the member 76 may be suitably modified to have a maximumdiameter less than the opening 130 or, in the alternative, the member 76may be divided into two portions, as indicated by the dotted line 132 inFIG. 4, both of these portions having a D-shaped opening similar to theopening 78 so that the outer knob portion may be placed on the selectorshaft 56 after the units dial 86 has been positioned behind the frontpanel 36a. When the panel 36a is positioned outside the tens and unitsdiscs the pin 96 on the member 90 is still positioned in the hole 100 ofthe wall 50 so that the member 90 is prevented from rotating.

As stated above, the channel selector shaft 56 is rotated seven fullrevolutions to cover the entire UHF band. In accordance with the presentinvention, a positive stop arrangement is provided for the shaft 56 ateach end of its travel so as to prevent display of channel numbersbeyond the UHF band, i.e., lower than channel 14 or higher than channel83, in the viewing area 126. A stop mechanism which positively preventsthe display of such numbers is important so that the operator does notbecome confused when he sees an unassigned channel number and attempt toturn the knob in the wrong direction with resultant damage to themechanism. In the arrangement of the present invention, the channelselector shaft 56 is prevented from axial movement by means of a Cwasher 132 which is positioned adjacent the chassis wall 50 and a collar134 which is positioned on the other side of the wall 50 and is securedto the channel selector shaft 56 by means of a suitable set screw or thelike. The collar 134 rotates with the channel selector shaft 56 andcarries a stop pin 136 which projects radially outwardly from the collar134. The outer surface of the channel selector shaft 56 is provided witha series of threads 138 which control movement of a follower nut 140provided with an internal threaded opening in engagement with thethreads 138. The nut 140, which may be a split nut the two halves ofwhich are held together by a set screw, or the like, is provided with anextension portion 142 (FIG. 10) which has a slot 144 in the end thereofwhich is adapted to receive an upturned flange portion 146 which isstruck out of the base member 32. Accordingly, the nut 140 is preventedfrom rotating and as the channel selector shaft 56 is rotated the nut140 moves along the threads 138 at a rate determined by the pitch ofthese threads. The nut 140 carries a pin 148 which projects from bothsides of the nut 140 and extends parallel to the selector shaft 56. Asecond collar 150 is also secured to the selector shaft 56 by means of aset screw 152 and rotates with this shaft, the collar 150 carrying aforwardly projecting pin 154. When the selector shaft 56 has been movedto the channel 83 detent position at the upper end of the UHF band, thenut 140 has been moved forwardly by an amount sufficient that the pin136 on the collar 134 is positioned adjacent to but not against the pin148 on the nut 140, as shown in FIG. 7, sufficient clearance beingprovided between the pins 136 and 148 to permit positive seating of thedetent spring 70 between the lobes of the wheel 72 in the channel 83detent position thereof. However, when the operator attempts to turn thechannel selector shaft 56 in a clockwise direction, the pin 148positively prevents further movement of the shaft 56 by an amountsufficient to bring the next units numeral 88 into the area 126. Sincethe shaft 56 rotates 36° between detent positions and the units dial 86is directly connected thereto, engagement of the pins 136 and 148 iseffective to prevent the next numeral 88 from being seen by theoperator.

When the channel selector shaft 56 is rotated one full revolution awayfrom the channel 83 position, the nut 140 has been moved rearwardly byan amount sufficient that the pin 136 on the collar 134 misses the pin148, as shown in FIG. 8. Accordingly, the selector shaft is unrestrainedand may be moved through another six revolutions during which the nut140 is moved rearwardly to the position shown in FIG. 9. When theselector shaft 56 has been moved to this channel 14 position the rearend of the pin 148 is positioned adjacent the pin 154 carried by thecollar 150. Accordingly, if the operator attempts to move the selectorshaft 56 in a counterclockwise direction, the pin 154 engages the rearend of the pin 148 and positively prevents movement of the selectorshaft 56 by an amount sufficient to bring the next units numeral 88 intoviewing position. In this connection, it will be noted that the stopmechanism of the present invention, and specifically the pins 136 and154, are an integral part of the selector shaft 56 and move with thisshaft until interference with the pin 148 occurs. Furthermore, the unitsdial 86 is mounted on and rotates as an integral part of the selectorshaft 56 so that the stop action produced by interference with the pin148 directly controls the position of the units disc 86. As a result,the units disc 86 is positively prevented from rotating by an amountsufficient to prevent the display of the next digit 88.

While the selector shaft 56 is accurately positioned by engagement ofthe torsion spring portion 70 with the index wheel portion 72 of theshaft 56, it is necessary to transmit this detent position to the rotorshaft 58 of the UHF tuner 42 with a high degree of accuracy.Furthermore, since the selector shaft 56 rotates seven revolutions tocover the entire UHF band it is also necessary to provide a step-downgearing arrangement between selector shaft 56 and the rotor shaft 58since the rotor shaft 58 rotates somewhat less than 180° to cover theentire UHF band. To this end, the selector shaft 56 is provided with aradially extending flange portion 160 at the rear end thereof, thisflange portion having a rearwardly extending annular face which acts asa clutch face on which is positioned a clutch pad 162. The fine tuningshaft 54 is provided with a rear end portion 164 which has a double Dcross section and a gear member 166 is mounted on the end portion 164and has an opening therein which matches the double D cross section ofthe end portion 164 so that the gear 166 rotates with the shaft 54.

The gear 166 is provided with a forwardly extending skirt portion 168(FIG. 4) which forms a recess within which is positioned the extremerear end 170 of the selector shaft 56, the forward end face of the skirtportion 168 forming a second clutch surface which is held in engagementwith the clutch pad 162 by means of a coil spring 172 which ispositioned between the rear surface of the gear 166 and a washer 174carried on the end of the fine tuning shaft 54. The forward end of thefine tuning shaft 54 is held against the forward end of the selectorshaft 56 by means of a C washer 176 so that the spring 172 is effectiveto hold the gear 166 in engagement with the selector shaft 56 throughthe clutch pad 162. Accordingly, as the selector shaft 56 is rotated bymanipulation of the knob portion 84, the gear 166 rotates in exactregistration therewith.

A relatively large gear 178 is rotatably mounted on a post 180 which ismounted on the rear wall 40 of the base plate 32 (FIG. 3). A small gear182 is also rotatably mounted on the post 180 and rotates with the gear178.

Preferably, the gears 178 and 182 are molded as a single integral unitof plastic material, this gear being retained on the upper end of thepost 180, which is of reduced cross section, by means of the C washer184. Another large gear 186 is mounted on the rotor shaft 58 of the UHFtuner 42 by means of a set screw 188 provided in the hub portion of thegear 186. The teeth of the gear 186 being in mesh with the teeth of thegear 182.

The gear ratios of the gear pairs 166, 178 and 182, 186 are chosen suchthat the required step-down ratio, of approximately 14 to 1, is providedbetween the selector shaft 56 and the UHF rotor shaft 58. Furthermore,in accordance with an important aspect of the present invention, thegears 166, 178, 182 and 186 are purposely positioned relative to oneanother so that the gear teeth thereof are loosely meshed. The rotorshaft 58 is also spring loaded in one direction. With such anarrangement it has been found that the step-down ratio of gearing to therotor 58 acts to magnify or multiply the accuracy with which the detentwheel portion 72 of the selector shaft 56 is positioned. Thus, if thedetent wheel 72 is resettable to 1.0° by the action of the end portion70 of the torsion spring 60 thereon, the rotor shaft is reset inaccordance with the present invention to 1/14 of that amount or 0.071°.

However, this extremely precise reset action is not obtainable if eitherthe spring loading in one direction is eliminated, or if the gears whichform the gear train are engaged on both sides of the teeth thereof, asin the case of scissors type gears which are normally used to eliminatebacklash. By employing spring loading in one direction from the rotorshaft 58 back through the gear pairs 186, 182 and 178, 166 to the detentwheel 72, the individual teeth of each gear act only as positioningmembers or levers and only one face of each tooth is engaged by thecorresponding face of the mating gear tooth of the other gear althoughthe selector shaft 56 may be rotated in either direction to reach aparticular UHF station. Thus, by mounting the gear sets 166, 178 and 182and 186 with the gear teeth thereof, quite loosely enmeshed, thestep-down gearing minimizes additional frictions, such as would beintroduced with scissors type gears in which both sides of a gear toothare pinched by the opposing teeth of the other gears.

With the arrangement of the present invention the accuracy with whichthe detent wheel 72 is positioned by the torsion spring 60 is magnifiedby a factor equal to the step-down gear ratio, insofar as the rotorshaft 58 is concerned, provided the rotor shaft is spring loaded by anamount sufficient to maintain one face of the gear teeth in constantengagement. This biasing or loading force may be relatively light if thegears in the gear reduction train are freely rotatable on their bearingsso that the gears making up this gear train may be relativelyinexpensive plastic gears and yet will not be deformed or distorted in amanner which would reduce the detent accuracy and repeatability. As aresult, no strong forces are employed to obtain the desired accuracy ofdetent and the individual gear teeth of each gear merely act aspositioning levers which are constantly loaded in one direction. In FIG.2A a fragmentary portion of the gears 182 and 186 is shown on a greatlyexpanded scale. Referring to this figure, the gear 186 is constantlyurged in the direction of the arrow 190 by means of the spring loadingforce exerted on the rotor shaft 58, by means to be described in moredetail hereinafter. As a result of this constant biasing force, the face192 of the gear tooth 194 is continually held in engagement with theface 196 of the gear tooth 198 of the gear 182, and the opposite face200 of the gear tooth 194 is spaced a substantial distance 202 away fromthe corresponding face 204 of the adjacent gear tooth 206 of the gear182. If the selector shaft 56 is rotated so that the gear 182 moves in acounterclockwise direction, as viewed in FIG. 2A, the faces 192 and 196of the respective gear teeth of the gears 186 and 182, or correspondingfaces of the next pair of mating gear teeth, still remain in engagementdue to the fact that a biasing force is continually exerted on the gear186 in the direction of the arrow 190. In this connection it is alsoimportant to reset accuracy that the gears 178, 182, while being freelyrotatable as a unit on the post 180, be mounted on this post without anyplay or looseness in the bearing since any such play will directlyaffect the reset accuracy.

A similarly precise positioning is also accomplished between the looselymeshed gear teeth of the gears 178 and 166. Accordingly, no additionalfrictions are introduced by pinching of the individual gear teeth of thegears in the gear reduction train so that the accuracy of positioning ofthe detent wheel 72 is multiplied by the factor of the gear step-downratio due to the fact that the spring loading on the rotor shaft 58 canextend back through the entire step-down gear train and be effectiveprecisely to follow the detented position of the wheel 72.

In order to provide the above-discussed biasing or loading force for therotor shaft 58 so that one face of the teeth in the gear reduction trainwill remain in engagement for rotation of the selector shaft 56 ineither direction, the rotor shaft 58 is provided with an opening 208(FIG. 3) extending from the forward end thereof along the central axisof rotation to a point near the rear end thereof at which point atransverse slot 210 is provided. A torsion spring wire 212 is positionedwithin the opening 208 and is provided with an end portion which isreceived in the slot 210 so that the rear end of the spring 212 is fixedto and moves with the rotor shaft 58. The forward end of the spring 212extends out through the opening 208 and is provided with a right-angleend portion 214 which is hooked over one wall 216 of the UHF tunerhousing. The torsion spring 212 is so arranged that when one end thereofis positioned in the slot 210 and the other end is hooked over the wall216, a biasing force is exerted on the rotor shaft 58 and hence upon thegear 186 secured thereto. This biasing force is reflected back throughthe loosely meshed gear pairs 186, 182 and 178, 166 so that the rotorshaft 58 may be accurately and precisely positioned in accordance withthe setting of the detent wheel 72. It is also important that the rotorshaft 58 be very freely mounted in the tuner housing so that it canrespond very accurately to the positioning information transmitted to itthrough the step-down gear train from the detent wheel 72. To this end,the rear end of the shaft 58 is mounted in a spring tongue portion 209of a bracket 211 which is mounted on the inside of the tuner housing,the tongue 209 resiliently urging the forward end of the shaft 58against an opening in the opposite housing wall 216. Both portions ofthe shaft 58 which engage the tongue 209 and wall 216 are provided withconical bearings to minimize friction in the mounting of the shaft 58. Asimilar rotor shaft mounting and biasing arrangement is disclosed inBadget, et al. application Ser. No. 856,277 filed Sept. 9, 1969 andreference may be had to said application for the details of suchconstruction. It is also important that the UHF tuner housing be mountedin such a manner that forces exerted on the selector knob 84 by theoperator will not result in distortion of the tuner housing which canproduce frequency changes which interfere with reset accuracy. Bymounting the tuner 42 on the chassis 32 by means of the bolts 44 on onlyone wall thereof, distortion of the tuner housing and detuning inresponse to pressure on the selector shaft is minimized. However, itwill be understood that the tuner housing may be mounted on itssupporting chassis in other orientations as, for example, by securingone end wall of the housing to the chassis, and still minimize suchdetuning.

The above-described detent arrangement of the present invention, whileusing only ordinary and inexpensive plastic gears for the illustratedgears 166, 178, 182 and 186, and with the simple spring loading of thetorsion wire 212, has been found to give extremely good resetcharacteristics. The resettability of the tuner is determined byadjusting the selector shaft 56 away from a particular UHF channelposition to another channel position and then returning it to saidparticular channel position and noting how much the tuner is tuned awayfrom the exact same frequency as before.

Furthermore, this operation must be performed by changing only theposition of the selector shaft, as determined by the detent wheel 72,and without any fine tuning adjustment, AFC correction, or the like. Thedetent arrangement of the present invention provides a resettabilitywhich has substantially zero error at many points in the UHF band andwill vary a maximum from the previous frequency setting of only about150 kilocycles for any UHF channel within the UHF band. When it isconsidered that the UHF oscillator must be tuned to a frequency ofapproximately 931 megacycles at the upper end of the UHF band, it willbe seen that the detent arrangement of the present invention provides anaccuracy of approximately 160 parts per million maximum deviation, withthe deviation at many points within the UHF band being substantiallyzero reset error.

Manually tuned VHF tuners are factory aligned to the precise frequenciesof the assigned VHF channels to a very high degree of accuracy at eachdetent position of the selector shaft so that the VHF tuner operator isassured that the VHF station indicated by his dial is actually beingreceived. He may then use his manual fine tuning adjustment to get theparticular picture quality he desires. In order to provide a UHF tuningarrangement which is as nearly comparable with VHF tuners as possible,and in accordance with an important aspect of the present invention, theabove-described detent mechanism is utilized during the alignment of theUHF tuner 42 so that a linear timing curve is provided which willessentially match the linear motion established by the above-describeddetent mechanism as determined by the detent positions of the wheel 72.This linearity is preferably such that the tuning characteristic willhave a maximum deviation from the channel number indicated by the discs86 and 92 of plus or minus 3 megacycles so that a nonambiguous dialindication is achieved and the operator is assured that the UHF channelindicated by the dial is actually being received. In this connection, itwill be understood that the detent arrangement of the present invention,whereby greatly increased accuracy of reset is made possible, isnecessary in order to align the UHF oscillator tuning elements to adesired degree of accuracy. This is because the reset error is random incharacter and if this error is large, as was the case with previous UHFtuner designs, it is impossible to align the UHF tuning elements to agiven maximum deviation from linear. Although the tuning elements couldbe adjusted to give a certain frequency at a certain detent position ofthe selector shaft, there was no assurance that the next time thischannel was selected the shaft would not be reset to a differentposition which would result in a tuning frequency different from the oneoriginally established for that channel during alignment.

In the past, the RF and mixer sections of a continuously variable UHFtuner have been aligned and tracked by providing the rotor plates of thecapacitive portions of the RF and mixer sections of the tuner with aseries of radially extending slots whereby portions of the rotor platesof the variable capacitors can be adjusted by bending the same relativeto the fixed stator plate or plates in each section of the tuner. Theoscillator section of conventional UHF tuners is aligned only at certainpoints in the UHF band, such as at the high and low ends of the band anda chosen midpoint in the UHF band. The reason why the UHF oscillator didnot in the past have to be accurately and precisely aligned to each UHFstation over the entire band is that the fine tuning adjustment, in thecase of two speed drive mechanisms, or the preset memory tuningarrangement of detented preset UHF tuners could readily adapt to ratherlarge variations in the alignment curve of the tuner. However, thislarge variation in alignment which is conventionally plus or minus 18megacycles (i.e., the width of three UHF channels), was acceptable onlyin conjunction with an analog type dial which gave a dial indicationwhich was only a rough approximation of the channel being tuned.

While the conventional method of slotting the rotor plate and adjustingindividual rotor plate increments by bending has been entirely suitablefor the RF and mixer sections of the UHF tuner, when an attempt is madeto align the UHF tuner to the exact frequency of each of the 70 UHFchannels, and when it is realized that the total variation in movementof the rotor plates is somewhat less than 180°, it will be evident thatthe slotting of the rotor plates for individual UHF channel adjustmentis completely impractical and unworkable. In accordance with the presentinvention, the rotor plates of the UHF oscillator section of the tunerare not slotted, since slotting and bending of the rotor platesintroduces errors which cannot be exactly compensated for even bylaborious and time consuming individual channel alignment. On thecontrary, it has been found that the rotor and stator blades may besheared and punched by conventional die methods to a very high degree ofaccuracy if the blade contour is initially chosen to give a nominalizedlinear variation of oscillator frequency with rotation of the rotorshaft. On the other hand, nonlinearities occur due to other factorswhich, in accordance with an important aspect of the present invention,are corrected where they occur rather than by attempting to bend slottedrotor plates to compensate for these errors. Thus, considering theoscillator section of the tuner 42, as shown in FIG. 14, the oscillatortuning line comprises a sinuous metal conductor 220 which is physicallyconnected by soldering to a small fixed capacitor 222, as indicated bythe solder joint 224 in FIG. 14, so that a rigid mounting is providedfor one end of the line 220. The other end of the line 220 is formedintegrally with a stator plate portion 226 which extends between a pairof rotor plates 228 which are mounted on the rotor shaft 58. As therotor shaft 58 is rotated, the rotor plates 228 become more or lesscompletely aligned with the stator plate section 226 and hence alter thecapacity to ground at the upper end of the line 220, it being understoodthat the rotor shaft 58 is connected to ground at the adjacent wallpartitions of the UHF tuner housing. The upper end of the tuner line isconventionally supported from the upper wall 230 of the tuner housing bymeans of a post 232 of dielectric material, such connectionconventionally being made by means of a solder connection 234 between aflat section of the line 220 and the round post 232.

In assembling the tuner, the rotor plates 228 are first positioned inaccurately spaced grooves in the rotor shaft 58 by means of a mechanicaljig arrangement and these plates are then staked to the rotor shaft 58so that they are accurately positioned thereon. The rotor shaft 58 withrotor plates assembled is then positioned within the bearing seats inthe tuner housing and the stator plate portion 226 is aligned incorrectly spaced relation thereto.

With such a UHF oscillator tuning arrangement, various factors areeffective to influence the linearity of the tuning characteristic eventhough the rotor plates 228 are cut to a high degree of accuracy toconform to a nominalized linear contour with respect to the stator plate226. Thus, the stator plate portion 226 may vary in thickness, thedielectric properties of the post 232 may vary, the position of thispost 232 on the tuner wall may vary and more or less solder may be usedat the joint 234 which causes slight changes in capacity. Theseinaccuracies and tolerances are compensated for by means of a flat tabelement 236 which is secured to the tuner wall 230 by any suitablemeans, such as soldering, and is positioned in the vicinity of the post232 and may be bent toward or away from this post to provide very slightchanges in capacity. Accordingly, variation of the position or shape ofthe tab 236 may be employed to correct the tuner alignment curve at theupper end of the frequency band while still maintaining the highlyaccurate and linear effect of the accurately punched rotor plates 228.In a similar manner, a small adjustment member 238 is secured to theterminal of the fixed capacitor 222 adjacent the end portion of the line220 and is provided with a tab portion 240 which extends in closeproximity to the adjacent wall of the tuner housing. The portion 240 maybe adjusted to give slight variations in capacity at the lower end ofthe UHF band. In this connection it will be understood that the use of atrimming capacitor employing an adjustment screw would not besatisfactory because of the inductance introduced by the screw whichcauses spurious resonances in the UHF band. However, the thin flat tabs236 and 240 provide the desired capacity adjustment without introducingundesired inductance effects. Preferably, the fixed capacitor 222 has afixed capacitance value of approximately the same value as the capacityintroduced by the rotor plates 228 and the stator portion 226 when theserotor plates are fully closed, this value being usually in the order of10 picofarads. If desired, a midpoint adjustment may be made byproviding a small loop of wire 241 positioned adjacent the midportion ofthe tuning element 220, the ends of the loop 241 being soldered to thehousing wall to form a shorted turn inductance loop which may be movedtoward or away from the line 220 to provide for further adjustment ofthe tuning characteristic during alignment. In this connection it willbe understood that the unslotted rotor plates 226 may also be bentslightly at various points in the alignment procedure. However, suchbending will produce relatively gentle or gradual variations in thetuning characteristic rather than the abrupt variation or discontinuityproduced by bending one section of a slotted rotor plate.

While the UHF tuner of the present invention is preferably aligned inthe manner described above so as to have an extremely linear tuningcurve, it is still necessary to provide a separate fine tuningadjustement for the UHF tuner so that long term effects, such as thermaldrift, aging of components, and the like, may be compensated and theoperator can adjust the tuner at any indicated station to produce apicture of the desired characteristics. To this end, a fine tuning knob250 is secured to the forward end of the fine tuning shaft 54 bypositioning the same on a flat end portion 252 thereof. The gear 166 isprovided with an arcuate slot 254 (FIG. 11) which is adapted to receivea tongue-like projection 256 provided on the rear end portion 170 of thechannel selector shaft 56. The projection 256 and slot 254 thus form alost motion connection between the selector shaft 56 and the fine tuningshaft 54 which permits a limited movement of the fine tuning shaft 54,and hence of the gear 166, while the selector shaft 56 remains at aparticular detent position established by the wheel 72. Accordingly,when the fine tuning knob 250 is rotated the gear 166 is rotated whilethe clutch formed by the flange 160, the clutch pad 162, and the rearface of the gear 166 slips, so that the rotor shaft 58 may be adjustedby an amount equal to the movement of the tongue 256 within the slot 254without changing the detent position of the channel selector shaft 56 orthe setting of the dial discs 86 and 92. However, when the channelselector knob portion 84 is adjusted to a new UHF channel position, thegear 166 is carried to the new detent position established by the wheel72 since the spring 172 is strong enough to prevent the clutch 160, 162from slipping and the fine tuning shaft 54 rotates with the selectorshaft 56. Accordingly, at any detent position of the wheel 72, i.e., atany one of the UHF positions of the channel selector shaft 56, the finetuning knob 250 may be rotated by an amount determined by the arcuateslot 254 to provide a precise or fine tuning adjustment of the rotorshaft 58.

While the above-described fine tuning arrangement is effective to permitthe customer to make a fine tuning adjustment at any UHF channelposition of the selector shaft 56, the fine tuning knob 250 ispositioned inside of the selector knob 84, whereas in conventional VHFfine tuning knob is positioned concentrically outside of the channelselector knob. In accordance with a further aspect of the invention,either of two different arrangements may be employed to provide a finetuning knob arrangement which is concentric with and outside of thechannel selector knob. One such arrangement is shown in FIGS. 15 and 16and may be employed instead of the shaft and knob arrangement shown inthe embodiment of FIGS. 1 to 14, inclusive.

Referring to FIGS. 15 and 16, wherein similar reference numerals havebeen given to elements corresponding to those previously discussed inconnection with the embodiment of FIGS. 1 to 14, inclusive, the unitsdisc 86 is secured to the forward end of the channel selector shaft 56,in the manner described heretofore, and a hub portion 260 is providedintegrally therewith which extends forwardly of the units disc 86 and isprovided with a pair of diametrically opposed openings 262 therein whichare adapted to receive a pair of rearwardly extending pins 264 which areconnected to the centrally located channel selector knob 266. A finetuning knob 268 is provided with a pair of arcuate slots 270 throughwhich the pins 264 extend, thereby permitting a limited arcuate movementof the fine tuning knob 268 by grasping the knurled peripheral edgeportion thereby which projects beyond the periphery of the channelselector knob 266. With this arrangement the channel selector knob 266may be rotated to any desired UHF channel position and carries the finetuning shaft 54 and knob 268 with it, as in the embodiment of FIGS. 1 to14, inclusive, because the clutch 160, 162 does not slip under theseconditions. However, after the channel selector knob 266 has been movedto a desired UHF channel position, the fine tuning knob 268 may berotated independently of the knob 266 until the pins 264 strike the endsof the arcuate slots 270. A limited motion of the fine tuning shaft 54is thus permitted in the arrangement of FIGS. 15 and 16, while providingconcentric fine tuning in which the fine tuning knob is outside of thechannel selector knob and may be adjusted independently of such channelselector knob. Further support for the channel selector knob 266 isprovided by means of a forwardly projecting pin portion 272 at thecenter of the fine tuning knob 268, which fits into a correspondingrecess in the rear face of the channel selector knob 266. As indicatedin FIG. 16, the numerals on the tens and units discs 86 and 92 arearranged at a suitable radius to permit these numerals to be readilyvisible to the operator beyond the periphery of the fine tuning knob268.

In FIGS. 17 and 18 an alternative selector knob and fine tuning knobarrangement is employed which may be substituted for the arrangementshown in the embodiment of FIGS. 1 to 14, inclusive, or the embodimentof FIGS. 15 and 16. Again, similar reference numerals have been employedfor elements corresponding to previously discussed embodiments.

Referring to FIGS. 17 and 18, a shaft reversal arrangement is employedtherein which permits the units dial 86 and tens dial 92 to bepositioned behind the front panel 276 of the television cabinet, thisfront panel being provided with a viewing window 278 through which thetens and units numerals of the above-described UHF dial indicatorarrangement may be seen. In this embodiment, a transversely extendingpin 280 is secured to the forward end of the fine tuning shaft 54 andextends through a transverse slot 282 formed in the forward end of thechannel selector shaft 56 ahead of the units disc portion 86. A channelextension shaft 284 is press fitted into an opening 286 in the end ofthe selector shaft 56, the extension shaft 284 being provided with aflat 288 on the forward end thereof which is adapted to receive achannel selector knob 290. The pin 280 also extends through alongitudinally extending slot 292 which is formed in the rear skirtportion 294 of a fine tuning extension shaft 296, this extension beingprovided with a flat 298 which is adapted to receive an outer concentricfine tuning knob 300. The shaft extension 296 is retained in place by aretaining ring 302 in the forward direction and by engagement of theoffset portion 304 thereof with the forward end of the channel selectorshaft 56 in the other direction. In the embodiment of FIGS. 17 and 18,when the channel selector shaft extension 284 is rotated by means of theknob 290 the channel selector shaft 56 is directly rotated to thedesired UHF channel position due to the direct connection of theextension 284 to the shaft 56. However, when a fine tuning operation isto be performed at a particular UHF station, rotation of the knob 300 iseffective to rotate the fine tuning shaft 54 by engagement of the pin280 with one of the sides of the slot 292, this rotation beingindependent of the channel selector shaft 56 since the pin 280 can movewithin the arcuate slot 282 without moving the shaft 56. A fine tuningadjustment is thus effected in the manner described in detail heretoforein connection with the embodiment of FIGS. 1 to 14, inclusive.

The UHF tuner of the present invention may also be equipped to functionwith conventional automatic frequency control (AFC) or automatic finetuning (AFT) circuits in the associated television receiver by providinga variable capacity diode across the tuned circuit of the oscillatordescribed in detail heretofore in connection with FIG. 14 of thedrawings, as will be readily understood by those skilled in the art.Furthermore, when the accurate detent mechanism of the present inventionis employed in conjunction with a UHF tuner having a linear alignmentcurve, as described heretofore, the AFC diode will function to bring theUHF tuner into exact tune with any one of the UHF channels at aparticular detent position established by the wheel 72 so that anoperation comparable with the memory or preset type of UHF tuner may beachieved while permitting the selection of any channel in the UHF bandand a nonambiguous dial indication of the exact channel selected.

In this connection it will be understood that the normal pull-in rangeof an AFC control circuit is considerably less than three megacycles(the maximum alignment deviation discussed above) and is conventionallyabout 1.2 megacycles. However, the UHF channels received in a particulararea are usually grouped in a frequency range which is much smaller thanthe total UHF band. Accordingly, when the UHF tuner is aligned in themanner described above to have a gently varying alignmentcharacteristic, the manual fine tuning may be adjusted for a desiredpicture at any one of the receivable stations in that area and the AFCcontrol circuit will have sufficient range to pull-in to exact tuningthe other stations receivable in that area. This is because thegradually varying alingnment curve, which is free from suddennonlinearities, will insure that other stations relatively close to theone at which the fine tuning operation was performed will be much closerto exact alignment than three magacycles.

However, when AFC control of the UHF oscillator is employed to providethe equivalent of mechanically preset memory UHF tuners, it is desirableto disconnect or defeat the AFC control voltage during the manual finetuning operation so that tuning can be optimized at any particular UHFstation without any arbitrary corrective influences due to the AFCcontrol circuit. In such instance it is desirable to require the manualfine tuning operation to be performed by a unique manipulation of thefine tuning knob by the operator which can be utilized to defeat the AFCcontrol circuit.

In FIGS. 19-22, an alternative embodiment of the present invention isdisclosed wherein the UHF tuner is arranged to function with an AFCcontrol voltage from the associated receiver and the AFC control lead isdefeated or disabled during the manual fine tuning operation.Furthermore, the AFC control circuit is defeated each time the channelselector knob is moved to a different UHF channel so that pull-in by theAFC control circuit to an adjacent channel not corresponding to the oneindicated is prevented. More particularly, in the arrangement of FIGS.19 to 22, inclusive, the fine tuning shaft 54 is arranged to be pushedinwardly by the operator when a manual fine tuning operation is to beperformed, this rearward movement of the fine tuning shaft 54 beingemployed to actuate an AFC defeat switch. Thus, the rear end portion 310of the fine tuning shaft 54 is made of circular cross section so that itcan rotate freely within the gear 166.

The fine tuning shaft 54 is also provided with a concentric gear portion312 which is positioned between the main body of the shaft 54 and thereduced end section 310 thereof. A coil spring 314 is positioned betweenthe end of the selector shaft 56 and a retaining ring 316 on the forwardend of the fine tuning shaft 54, the spring 314 acting normally to urgethe fine tuning shaft 54 to a forward position shown in FIG. 20 in whichthe gear 312 is out of mesh with a series of planetary gears 318 whichare mounted on the posts 320 carried by the gear 166, the planetarygears 318 being positioned within a forwardly opening recess 322 in thegear 166. A coil spring 324 is positioned between the end of the gear166 and a collar 326 secured to the end portion 310 of the fine tuningshaft 54, the spring 324 being weaker than the spring 312 butsufficiently strong that the clutch comprising the flange 160, theclutch pad 162 and the forward annular face of the gear 166 does notslip as the selector shaft 56 is rotated.

When the selector shaft 56 is rotated to different UHF channelpositions, the fine tuning shaft 54 may remain stationary or may ridewith the channel selector shaft 56 if substantial frictions between thegear 166 and the end portion 310 are experienced. However, when theselector shaft 56 has been adjusted to a particular UHF channelposition, the fine tuning shaft 54 may be moved rearwardly by theoperator to the position shown in FIG. 22 so that the sun gear 312 ismoved into engagement with the planetary gears 318. The operator thenrotates the shaft 54 while in this rearward position so as to cause arotation of the gear 166 while the clutch 160, 162 slips because thespring 324 is relaxed when the shaft 54 is moved to the rear positionshown in FIG. 22. The ratio at which the gear 166 is driven in responseto rotation of the shaft 54 may also be chosen to give any desired ratioof movement of the rotor shaft 58 in response to a given angularmovement of the fine tuning shaft 54.

When the fine tuning shaft 54 is moved rearwardly, one spring arm 328 ofan AFC defeat switch 330 is moved rearwardly by engagement of the endportion 310 therewith so that the contact 332 (FIG. 20) carried therebyengages a corresponding contact carried by the switch arm 334. When thecontacts of the switch 330 are closed the AFC control voltage may beeither short circuited or grounded so that the AFC control circuit ofthe associated receiver is no longer effective to control tuning of theUHF oscillator. Accordingly, during the period when the fine tuningshaft 54 is rotated to effect a manual fine tuning operation of the UHFoscillator the associated AFC control circuit is defeated.

In the embodiment of FIGS. 19 to 22, inclusive, the AFC control circuitis also defeated each time the channel selector shaft 56 is moved to adifferent UHF channel position. More particularly, in the embodiment ofFIGS. 19 to 22, inclusive, the tip portion 336 of the torsion spring 60is positioned beneath the bottom spring contact 338 of a second AFCdefeat switch 340 having an upper spring contact 342, the contactscarried by the arms 338 and 342 being normally open when the V-shapedend portion 70 of the torsion spring 60 is positioned within one of thenotches in the detent wheel 72, as shown in FIG. 19. When the channelselector shaft 56 is rotated to another UHF channel position, theadjacent lobe on the detent wheel 72 raises the end portion 336 of thetorsion spring 60 so that the contacts carried by the spring arms 338and 342 are closed. Closure of these switch contacts is again employedto short circuit or ground the AFC control voltage so that the UHFoscillator is not subjected to the influence of the AFC control voltagewhile a new UHF channel is being selected. However, as soon as theV-shaped portion 70 falls into the selected notch of the detent wheel72, the contacts carried by the spring arms 338 and 342 are opened andAFC control is restored. The defeat switch 340 is conveniently mountedon a rearwardly extending portion 344 of the chassis wall 46 and thedefeat switch 330 is mounted on a depending end portion 346 of thebracket portion 344.

In FIGS. 23 and 24 of the drawings a further alternative embodiment ofthe invention is disclosed wherein a common AFC defeat switch 350 isactuated in response to both a push-to-engage fine tuning operation or achannel selection in response to rotation of the channel selector shaft56. Referring to these figures, wherein similar reference numerals areemployed for elements common to the embodiment of FIGS. 19 to 22,inclusive, the torsion spring 60 is provided with a rearwardly extendingright angle end portion 352 which extends through a vertically extendingslot 354 provided in a control member 356 which is rotatably mounted ona post 358 secured to the chassis wall 46. A cone shaped camming member360 is secured to the end portion 310 of the fine tuning shaft 54, thecone shaped member being provided with a forwardly opening recess 362within which is positioned a coil spring 364 which maintains the clutch160, 162 normally effective to rotate the gear 166 in response torotation of the channel selector shaft 56. The member 360 is retained onthe end portion 310 by means of the retaining washers 365 and 367.

When the fine tuning shaft 54 is moved rearwardly from the positionshown in FIG. 24, the gear 312 engages the gears 318 and effects a finetuning operation in the manner described heretofore in connection withFIGS. 19 to 22, inclusive. Also, when the shaft 54 is moved rearwardlythe cam member 360 moves with the shaft 54 and pivots the control member356 about the post 358 so that a projection 366 on the upper edge of thecontrol member 356 is effective to move the spring arm 368 of the switch350 upwardly and close the contacts carried by the spring arms 368 and370 thereof. When the fine tuning operation is completed and the shaft54 is released, the spring 314 moves the fine tuning shaft forwardly andthe cam member 360 is withdrawn so that the control member 356 movesback to the position shown in FIG. 23 and the switch 350 is opened.Closure of the switch 350 is employed to effect disabling of the AFCcircuit of the associated receiver in the manner described in detailheretofore.

When the channel selector shaft 56 is rotated, the end portion 352 ofthe torsion spring 60 is moved upwardly and also functions to pivot thecontrol member 356 about the post 358 so that the contacts of the switch350 are closed. Again, the AFC control voltage is short circuited orgrounded so that the AFC control voltage is no longer effective tocontrol the tuning of the UHF oscillator during selection of a new UHFchannel. However, the control member 356 may be moved upwardly during afine tuning operation without moving the torsion spring 60 since theslot 354 permits such upward movement without disturbing the position ofthe V-shaped portion 70 of the torsion spring 60. Accordingly, theabove-described detent action is maintained during the UHF fine tuningoperation while employing only the single AFC defeat switch 350 in theembodiment of FIGS. 23 and 24.

In FIGS. 25 and 26, a further alternative embodiment of the presentinvention is disclosed wherein an electronic fine tuning arrangement isemployed instead of the mechanical ones described heretofore. Referringto FIGS. 25 and 26, wherein similar reference numerals are employed, apotentiometer indicated generally as 372 is mounted on a bracketextension 374 of the chassis wall 46 and the rotary shaft 376 thereof isconnected to the end portion 310 of the fine tuning shaft 54, which isof circular cross section. A universal coupling indicated generally at378 is provided to interconnect the shafts 310 and 376, the coupling 378having a first bushing 380 secured to the shaft portion 310 and a secondbushing 382 connected to the potentiometer shaft 376. The potentiometer372 is provided with the terminals 384 and 386 connected to the ends ofthe potentiometer winding, and a terminal 388 connected to the slider ofthis potentiometer.

In FIG. 25, the potentiometer 372 is shown connected across a balancedunidirectional control voltage source, illustrated by the batteries 390and 392, the junction of these batteries being connected ground so thatmovement of the potentiometer arm varies the voltage at the terminal 388above and below ground. This terminal is connected through a resistor394 to one side of an AFC control diode 396, the other side of thisdiode being connected through a resistor 398 to a terminal 400 to whichthe conventional AFC control voltage is supplied from the associatedtelevision receiver. The diode 396 is connected across the inductanceelement 220 and variable capacitance element 228, which form the tankcircuit of the transistor oscillator 402, through the isolatingcapacitors 404 and 406. In the embodiment of FIGS. 25 and 26, thepotentiometer 372 is not moved while different UHF channels are beingselected by manipulation of the channel selector shaft 56 since the gear166 simply rotates about the cylindrical end portion 310 of the finetuning shaft 54, the clutch 160, 162 of previous embodiments beingeliminated. However, when a fine tuning operation is to be performedmanually, at a particular UHF station, the shaft 54 is rotated so thatthe potentiometer 372 is adjusted to provide a different D.C. voltagefor the AFC diode 396, thereby effecting a fine tuning operation of theUHF oscillater 402 in a manner understood by those skilled in the art.Any desired range of fine tuning may be provided by varying the voltagerange over which the potentiometer 372 may be adjusted, as will bereadily understood by those skilled in the art.

In FIGS. 27 and 28 of the drawings, an alternative arrangement is shownfor exerting the above-described loading or biasing force on the rotorshaft 58. Referring to these figures, the rotor shaft 58 in theembodiment of FIGS. 27 and 28 is solid and a coil spring 440 is employedexternally of the UHF tuner housing to exert the desired spring loadingeffect on this shaft. More particularly, a coil spring 440 is positionedbetween the gear 186 and the rear end of the UHF tuner housing, thebottom turns of the coil spring 440 being positioned within anupstanding collar or centering sleeve 442 which is secured to theadjacent tuner housing wall by means of the solder joints 450.

The upper end of the coil spring 440 is provided with a right angle endportion 446 which is insertable in a suitable opening in the gear 186,as shown in FIG. 27, the uppermost turn of the spring 440 beingpositioned by a flange portion 444 which is of a larger diameter thanthe remaining hub portion of the gear 186, so that the remaining turnsof the spring 440 do not touch this hub as the gear 186 is rotated. Thebottom end 448 of the coil spring 440 is positioned within a slot in thecollar 442, as shown in FIG. 28, so that the bottom end of the coilspring 440 is restrained while the top end of this coil spring rotateswith the gear 186. If desired, a number of similar slots may be providedaround the periphery of the collar 442 so that the end position 448 maybe readily adjusted to any desired mount of loading of the shaft 58 bypositioning the end 448 in the appropriate one of said slots.

The inner diameter of the sleeve 442 is just slightly larger than thebottom turns of the coil spring 440 so that this sleeve acts as acentering device to prevent the turns of the spring 440 from engagingthe hub of the gear 186 as the rotor shaft 58 is moved throughapproximately 180° during tuning to various stations in the UHF band. Ithas been found that if the turns of the coil spring 440 are permitted totouch the hub portion of the gear 186 at any point, during the rotationof the shaft 58, undesired side thrust is exerted on this shaft whichcan seriously interfere with the precise reset characteristics of thedetent mechanism described heretofore in connection with the embodimentof FIGS. 1 to 14, inclusive.

While the torsion spring 212 (FIG. 3) of the embodiment of FIGS. 1 to14, inclusive, also avoids such side thrust, the provision of the hole208 in the rotor shaft 58 is quite expensive whereas in the springloading embodiment of FIGS. 27 and 28 the rotor shaft 58 may be solidand hence considerably less expensive than the arrangement shown in FIG.3.

In certain instances a minimal frontal area for the UHF tuner isdesirable in connection with a particular design of television receiver.In the embodiment of FIGS. 29 and 30 an arrangement is provided wherebythe frontal area of the UHF tuner mechanism and particularly the UHFdial arrangement is minimized. Referring to FIGS. 29 and 30 whereincorresponding numerals have been employed for elements similar to thosedescribed previously in connection with the embodiment of FIGS. 1 to 14,inclusive, a decade dial arrangement is provided which comprises a unitsdial 426 and a tens dial 424, the numbers for these dials appearing onthe periphery of a pair of counter wheels which are aligned vertically,the wheel 426 being mounted on a shaft 422 which is carried by thebracket portions 414 and 416 of the main chassis 32, and the wheel 424being rotatably mounted on the shaft 422 and spaced above the wheel 426.

A first bevel gear 410 is secured to the channel selector shaft 56 aheadof the forward end of the torsion spring 60 and is in engagement with abevel gear 412 secured to the vertically positioned shaft 422. The unitsdial 426 is secured to and rotates with the shaft 422, this dial makingone revolution for each revolution of the selector shaft 56. A trippinion 428 is mounted on a shaft 430 which is positioned between theupper and lower bracket members 414 and 416, the trip pinion 428 havingteeth which engage with corresponding teeth on the tens dial 424 andbeing rotated one tens digit increment for each revolution of the unitsdial 426 by means of tripper teeth similar to the teeth 116 in theembodiment described heretofore in connection with FIGS. 1 to 14,inclusive.

In the embodiments of FIGS. 29 and 30 the channel selector shaft 56extends out through an opening in the front panel 418 of the televisioncabinet, a channel selector knob 432 being secured to the forward end ofthis shaft outside the front panel 418. Also, the fine tuning shaft 54extends outwardly beyond the channel selector shaft 56 and a fine tuningknob 434 is secured to the end of the shaft 54. The panel 418 isprovided with an opening 420 through which the vertically aligned tensand units digits and the dials 424 and 426, respectively, are visible sothat a nonambiguous digital dial indication of the UHF channel beingreceived is provided. If desired, these digits may be illuminated by asuitable indicator lamp positioned behind the panel 418.

As will be evident from FIG. 30, the frontal area of the arrangement ofFIGS. 29 and 30 is extremely small, since the UHF tuner 42 is positionedon edge and the dials 424 and 426 occupy a very small amount of frontalarea of the television cabinet. In this connection it will be understoodthat the dials 424 and 426 may be of even smaller diameter than shown inFIGS. 29 and 30 and the tens and units digits appearing thereon may bemade larger than shown in these figures so that an extremely compact UHFdial indicator arrangement may be provided. In other respects, theembodiment of FIGS. 29 and 30 is similar to the arrangement described indetail heretofore in connection with FIGS. 1 to 14, inclusive.

While there have been illustrated and described various embodiments ofthe present invention, it will be apparent that various changes andmodifications thereof will occur to those skilled in the art. It isintended in the appended claims to cover all such changes andmodifications as fall within the true spirit and scope of the presentinvention.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. The combination of a UHF tuner having acontinuously variable main tuning shaft rotation of which is effectiveselectively to receive signals on all channels in the UHF televisionband, a station selector shaft, gear means providing a step-down drivingratio on the order of 14:1 interconnecting said selector shaft and saidmain tuning shaft, detect means mounted directly on said selector shaftto establish a stop position of said main tuning shaft via said gearmeans for each of the television stations in the UHF television band,means for providing a unique indication of the channel to which thetuner is tuned, a vehicle impedance element electrically coupled to saidUHF tuner, said variable impedance element being responsive to anelectrical control signal for altering the tuning of said UHF tuner, afine tuning shaft, and a control element mechanically coupled to saidfine tuning shaft and responsive to the position of said fine tuningshaft for providing a control signal to said variable impedance elementto effectively fine tune said UHF tuner independently of said maintuning shaft.
 2. The combination recited in claim 1 wherein saidvariable impedance element includes a voltage variable capacitor.
 3. Thecombination recited in claim 1 wherein said voltage variable capacitoris a voltage variable capacitance diode.
 4. The combination recited inclaim 3 wherein said voltage variable capacitance diode is an AFCcontrol diode.
 5. The combination recited in claim 3 wherein said tunerincludes an oscillator transistor and said voltage variable capacitancediode is electrically coupled to said oscillator transistor for varyingthe frequency of oscillation thereof.
 6. The combination recited inclaim 1 wherein said control element includes a potentiometer having apotentiometer control shaft mechanically coupled to said fine tuningshaft.
 7. The combination recited in claim 6 wherein said potentiometeris electrically connectable to a source of direct current potential andis electrically coupled to said variable impedance element.
 8. Thecombination of a UHF tuner having a continuously variable main tuningshaft rotation of which is effective selectively to receive signals onall channels in the UHF television band, a station selector shaft,step-down driving means interconnecting said selector shaft and saidmain tuning shaft and imparting rotary motion from said selector shaftto said main tuning shaft, said step-down driving means being effectiveto rotate said tuning shaft approximately 180° for each seven rotationsof said selector shaft, detent means affixed directly to said selectorshaft for establishing a stop position of said main tuning shaft throughsaid step-down means for each of the television stations in the UHFband, an indicator providing a unique indication of each channel, avariable frequency oscillator having a frequency of oscillation that isadjustable over a range of frequencies corresponding to the entire UHFtelevision band upon rotation of said main tuning shaft for determiningthe frequency of the signal received by said UHF tuner, a voltagevariable capacitor electrically coupled to said oscillator for adjustingthe frequency of oscillation of said oscillator independently of theposition of said main tuning shaft to effect fine tuning of said tuner,a fine tuning shaft, and a control element coupled to said fine tuningshaft and to said voltage variable capacitor, said control element beingresponsive to the position of said fine tuning shaft for altering thecapacitance of said voltage variable capacitor to thereby adjust thefrequency of said oscillator to effectively fine tune said UHF tunerwithout moving said main tuning shaft.
 9. The combination recited inclaim 8 wherein said control element includes a variable voltage sourceelectrically coupled to said voltage variable capacitor and responsiveto rotation of said fine tuning shaft for adjusting the impedance ofsaid voltage variable capacitor.
 10. The combination recited in claim 8wherein said control element includes a potentiometer electricallycoupled to said voltage variable capacitor and mechanically coupled tosaid fine tuning shaft.
 11. The combination recited in claim 8 whereinsaid voltage variable source includes an automatic frequency controlvoltage source.
 12. The combination of, a UHF tuner having an oscillatorand RF and mixer sections, a plurality of groups of tuning elementsconnected to a common rotatable main tuning shaft, each of said groupsof tuning elements being operative to tune one of said oscillator and RFand mixer sections, a station selector shaft, gear means providing astep-down driving ratio on the order of 14:1 interconnecting saidstation selector shaft and said main tuning shaft, detent means mounteddirectly on said station selector shaft for establishing a stop positionof said main tuning shaft for each of the television stations in the UHFband, dial indicator means connected to said station selector shaft andarranged to provide an exact digital indication of the UHF channelnumber corresponding to each one of the stop positions of said maintuning shaft, said tuning elements of said UHF tuner being aligned toreceive corresponding UHF stations at each of said stop positions ofsaid main tuning shaft with a maximum error of approximately 3megacycles, whereby the channel number indicated by said dial indicatormeans is essentially nonambiguous, said UHF tuner including a voltagevariable capacitor responsive to a control voltage applied thereto foradjusting the tuning of only said oscillator to thereby tune said UHFtuner over a range of frequencies corresponding to less than thefrequency separation between adjacent channels.